Morphological variability of achenes of some European populations of Lactuca serriola L.

This study focuses on the morphological variability of Lactuca serriola achenes in relation to eco-geographic features. Fifty L. serriola populations from four European countries, Czech Republic, Germany, the Netherlands and United Kingdom, were studied. Five morphological characters of the achenes - length and width of achene, length/width index, length of beak, and number of ribs - were evaluated. Significant differences exist in achene morphology of two leaf forms of L. serriola, forma serriola and forma integrifolia. Achenes of f. serriola are shorter, thinner, shorter beaked, lower length/width index, and higher number of ribs compared to f. integrifolia. There was significant variation in the measured characters. Statistical analysis indicated that achene length and width increased along an east-west transect from 2.95 to 3.35 mm and 0.93 to 1.00 mm, respectively. Mean beak length had a similar trend with the exception of German achenes. They had shorter beaks than achenes originating from the Czech Republic with 4.38 and Germany with 4.33 mm. The same trend was evident for L/W index from Czech with a ratio of 3.21 and Germany with 3.14. The number of ribs increased from east to the west in continental Europe, whereas the lowest number of ribs was recorded in achenes collected in Czech with 10.89 and the UK with 10.59. Achene morphology was significantly correlated with three eco-geographic features; longitude, latitude, soil texture of the habitats. The other eco-geographic factors, altitude and population size, did not significantly correlate with the studied characters of L. serriola achenes.     

Influence of Silver Colloid Presence on Stilbazolium Merocyanine Emission

Absorption, fluorescence emission, and fluorescence excitation spectra of stilbazolium merocyanine (1-(n-butyl)-4[(3,5-dimethoxy-4-oxocyclohexa-2,5-dienylidene)ethylidene]-1,4-dihydropyridyne) dye in water solution without and with colloidal silver addition were measured. In the presence of the colloid, besides the absorption band assigned to the protonated species of the dye (at 391 nm), an absorption band related to the free-base species appears at 490 nm. From the absorption and emission spectra, measured at various dye concentrations, follows that the aggregates are not effectively formed. Therefore, the long-wavelength absorption and fluorescence bands have to be related to some dye forms created by the solvatochromic effects. The fluorescence bands of the protonated and the free-base species are located at 559 nm and at about 630 nm, respectively. The shape of the long-wavelength band suggests the occurrence of more than one free-base form of the dye. At some dye and colloid concentrations, the global emission of the sample is enhanced as a result of silver addition. The increase in the emission yield of the dye could be partially due to not only the change in the concentrations of dye forms exhibiting various emission yields but is also due to the resonance surface plasmon effect. Because of the superposition of several effects, before the practical application of merocyanine as an indicator of metal presence in biological samples, its spectral properties in the system investigated should be established.     

Infectivity of Trypanosoma brucei Cultivated at 28 C with Tsetse Fly Salivary Glands*

SYNOPSIS. When transformed procyclic noninfective trypanosomes of several unrelated stocks of Trypanosoma brucei were cultivated in T-30 Falcon flasks at 28 C in a liquid medium containing head-salivary gland explants of Glossina morsitans morsitans some of the organisms developed into forms infective for mice. Infective trypanosomes were detected 7 to 14 days after the cultures were prepared and they persisted for varying periods of up to 88 days when the cultures were terminated. A few of the salivary glands became invaded with parasites about the time infective organisms appeared in the cultures. Using T. brucei TREU 929, it was shown that trypanosomes grown with between 27 and 50 explants were capable of producing infections consistently for prolonged periods. On the other hand, trypanosomes cultivated with 25 or fewer explants rarely infected mice. Infectivity titrations on trypanosome suspensions from cultures of stocks TREU 1275 and TREU 929 revealed that the maximum number of infective organisms was present 26 to 50 days after initiation of the cultures. Control cultures of trypanosomes grown in medium alone were generally not infective but 2 of the 6 stocks gave rise to a few sporadic infections. A few epimastigote-like and metacyclic-like trypanosomes were seen in stained preparations of infective inocula.     

Frequency of moulting by shore crabs Carcinus maenas (L.) changes their colour and their success in mating and physiological performance

Male shore crabs, Carcinus maenas [Linnaeus, 1758], compete aggressively for access to receptive females to mate. Size is the single most important factor for the outcome of these conflicts, large males with carapace width (CW) over 60 mm being much more likely to gain access to receptive females than smaller males. To compete aggressively, large male shore crabs decrease moulting frequencies and may potentially terminate moulting to enter a state of anecdysis, in which further growth is suspended to increase reproductive output. This change from a “growth” strategy to a “reproduction” strategy results in the creation of two morphs, which can roughly be separated by their colouration. As the new exoskeleton created during moult is always green in appearance, crabs tend to be green in appearance during periods where they grow rapidly and moult frequently. Green crabs are found in all size classes. However, as the exoskeleton becomes older, the colour gradually changes to a darker red colour, and large crabs that have spent an extended period in intermoult are therefore often red in appearance. Also, the exoskeleton of red crabs exhibits a higher incidence of epibionts and wear and tear. Red crabs can also be found in all size classes, but their relative proportion in the population increases dramatically in size classes above 60-mm CW. Size for size, the red morph has a thicker carapace and larger master chelae than the green morph. Also, the reproductive indices (RI) for red crabs are higher than for green crabs, and they experience higher mating success. However, this mating success appears to be achieved at the expense of a lower physiological tolerance, green crabs being better adapted to deal with changes in the surrounding environment. This increased tolerance is not only observed with regard to natural variations in the habitats where shore crabs live, but green crabs also appear to be more tolerant to variations caused by anthropogenic pollution. Consequently, the shift from growth to reproduction exerts a profound effect on the behaviour, physiology and ecotoxicology of male shore crabs. The present paper reviews the studies conducted so far, proposes a mechanism by which some of these differences between the two morphs are created and discusses their ecological and ecotoxicological significance.     

Acetate Oxidation by Bloodstream Forms of Trypanosoma cruzi*

Bloodstream forms of Trypanosoma cruzi had a substantial increase in respiration in the presence of acetate. Oxidation of acetate took place via the tricarboxylic acid cycle and involved an antimycin A-sensitive respiratory pathway. Oxygen uptake in the presence of acetate was as sensitive to antimycin A inhibition as was CO₂ production. There was a 6–7% residual O₂ uptake which was not inhibited by high antimycin concentrations. Human anti-T. cruzi sera had no effect on oxygen uptake.     

Multiple forms of carboxylesterase activity in Acinetobacter calcoaceticus

A carboxylesterase activity (E.C.3.1.1) was found in all four strains of Acinetobacter calcoaceticus tested. The activity was present in both 2 X 10(4) gav h-1 supernatant and bacterial wall-membrane fractions. The activity in the supernatant was in two molecular weight forms, the predominant form with a Mr of about 10(3) K and a minor form Mr approximately 600 K. The activity was inhibited by phenylmethylsulfonyl fluoride. SDS-PAGE showed that in A. calcoaceticus NCIB 8250 the activity was composed of three components of Mr 43, 40 and 38 K. The individual components showed different activities with 1- or 2-naphthyl esters. Of the other strains used, one showed a nearly identical pattern of component activities, while the other two showed only two component activities.     

Downregulation of neutral ceramidase by gemcitabine: Implications for cell cycle regulation

Gemcitabine (GMZ) is a chemotherapeutic agent with well established effects on cell growth arrest and apoptosis. In this study, we investigated the potential roles of bioactive sphingolipids in mediating the growth suppressing effects of GMZ on a polyoma middle T transformed murine endothelial cell line. After 12-hour GMZ (0.6 μM) treatment, cell growth was arrested at the G₀/G₁ phase as detected by flow cytometric cell cycle analysis and MTT cell viability analysis, and this was accompanied by dephosphorylation of the retinoblastoma protein (Rb). Furthermore, GMZ treatment resulted in increased levels of specifically the very long chain ceramides as determined by mass spectrometry. Mechanistically, GMZ did not appear to affect the activities of many enzymes of ceramide metabolism; however, GMZ caused a selective reduction in the protein levels of neutral ceramidase (NCDase), as indicated by Western blot analysis, with a concomitant decrease in NCDase activity. The significance of NCDase loss on cell cycle regulation was investigated by specific knockdown of the enzyme using small interfering RNA (siRNA). Interestingly, NCDase siRNA transfection was sufficient to induce a cell cycle arrest at G₀/G₁ and an increase in total ceramide levels, with significant elevation in very long chain ceramides (C_24:1 and C_24:0). NCDase siRNA also induced Rb dephosphorylation. These data provide evidence for a novel mechanism of action for GMZ and highlight downregulation of NCDase as a critical step in GMZ-mediated ceramide elevation and cell cycle arrest.     

Effect of Hinge Region State on Interaction of Human IgG3 with the Complement System

Covalently cross-linked rod-like dimers of human myeloma IgG3 are more efficient in the inhibition of the complement system reaction than compact dimers. This correlates with an increase in the stability of C_H2 domains of the immunoglobulin in the state with the rod-like hinge region.